With the conventional draw texturing machine, when a plurality of yarns are doubled, each yarn passes through separate heating spaces. To meet needs for more compact machines, a yarn heating apparatus that allows more than a yarn to pass through the same heating space was recently developed.
The construction of this newly developed yarn heating apparatus 3, however, is such that a first heat insulator 8 is packed in an outer case 7, an inner case 9 is provided inside the outer case 7, and a second heat insulator 11 provided with a heating space 10 is packed inside the inner case 9, as shown in the sectional view in FIG. 6. The bottom sides of the heating space 10 and the second heat insulator 11 are open and face the outside. A heating unit 13 comprising two buried sheath heaters 12 is provided in the heating space 10, and a middle heat insulator 14, which laterally divides the heating space 10 into two heating spaces 10a and 10b, is provided below the heating unit 13. A plurality of yarn guides 15 are placed with appropriate spacing in the two heating spaces 10a and 10b. The yarn guides 15 are mounted to the second heat insulator 11 on both sides of the heating space.
The above-described yarn heating apparatus 3, however, has a drawback, because the heating unit 13 is at some distance from the yarn which is guided by the inner groove 15a or the outer groove 15b of the yarn guide 15, the yarn cannot be heated sufficiently.